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authorIngo Molnar <mingo@kernel.org>2012-12-02 23:56:50 +0400
committerMel Gorman <mgorman@suse.de>2012-12-11 18:43:00 +0400
commit4fc3f1d66b1ef0d7b8dc11f4ff1cc510f78b37d6 (patch)
tree90baaa56f6b5244525c7637a14550f830486112a /include/linux/rmap.h
parent5a505085f043e8380f83610f79642853c051e2f1 (diff)
downloadlinux-4fc3f1d66b1ef0d7b8dc11f4ff1cc510f78b37d6.tar.xz
mm/rmap, migration: Make rmap_walk_anon() and try_to_unmap_anon() more scalable
rmap_walk_anon() and try_to_unmap_anon() appears to be too careful about locking the anon vma: while it needs protection against anon vma list modifications, it does not need exclusive access to the list itself. Transforming this exclusive lock to a read-locked rwsem removes a global lock from the hot path of page-migration intense threaded workloads which can cause pathological performance like this: 96.43% process 0 [kernel.kallsyms] [k] perf_trace_sched_switch | --- perf_trace_sched_switch __schedule schedule schedule_preempt_disabled __mutex_lock_common.isra.6 __mutex_lock_slowpath mutex_lock | |--50.61%-- rmap_walk | move_to_new_page | migrate_pages | migrate_misplaced_page | __do_numa_page.isra.69 | handle_pte_fault | handle_mm_fault | __do_page_fault | do_page_fault | page_fault | __memset_sse2 | | | --100.00%-- worker_thread | | | --100.00%-- start_thread | --49.39%-- page_lock_anon_vma try_to_unmap_anon try_to_unmap migrate_pages migrate_misplaced_page __do_numa_page.isra.69 handle_pte_fault handle_mm_fault __do_page_fault do_page_fault page_fault __memset_sse2 | --100.00%-- worker_thread start_thread With this change applied the profile is now nicely flat and there's no anon-vma related scheduling/blocking. Rename anon_vma_[un]lock() => anon_vma_[un]lock_write(), to make it clearer that it's an exclusive write-lock in that case - suggested by Rik van Riel. Suggested-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Turner <pjt@google.com> Cc: Lee Schermerhorn <Lee.Schermerhorn@hp.com> Cc: Christoph Lameter <cl@linux.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hugh Dickins <hughd@google.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Mel Gorman <mgorman@suse.de>
Diffstat (limited to 'include/linux/rmap.h')
-rw-r--r--include/linux/rmap.h17
1 files changed, 14 insertions, 3 deletions
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index f3f41d242e25..c20635c527a9 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -118,7 +118,7 @@ static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
up_write(&anon_vma->root->rwsem);
}
-static inline void anon_vma_lock(struct anon_vma *anon_vma)
+static inline void anon_vma_lock_write(struct anon_vma *anon_vma)
{
down_write(&anon_vma->root->rwsem);
}
@@ -128,6 +128,17 @@ static inline void anon_vma_unlock(struct anon_vma *anon_vma)
up_write(&anon_vma->root->rwsem);
}
+static inline void anon_vma_lock_read(struct anon_vma *anon_vma)
+{
+ down_read(&anon_vma->root->rwsem);
+}
+
+static inline void anon_vma_unlock_read(struct anon_vma *anon_vma)
+{
+ up_read(&anon_vma->root->rwsem);
+}
+
+
/*
* anon_vma helper functions.
*/
@@ -220,8 +231,8 @@ int try_to_munlock(struct page *);
/*
* Called by memory-failure.c to kill processes.
*/
-struct anon_vma *page_lock_anon_vma(struct page *page);
-void page_unlock_anon_vma(struct anon_vma *anon_vma);
+struct anon_vma *page_lock_anon_vma_read(struct page *page);
+void page_unlock_anon_vma_read(struct anon_vma *anon_vma);
int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);
/*